1. Field of the Invention
The present invention relates to an image pickup apparatus that controls exposure by a feedback control, and to a control method thereof.
2. Description of Related Art
A digital camera continuously captures images in advance and displays the captured images on a display device in order to determine exposure and focus prior to actual photographing.
During the display of a confirmation image before photographing, a brightness level of a subject is detected and a feedback control for controlling an exposure state is carried out to set the brightness level to a certain level. In the feedback control, one cycle (1 field=1 frame) of a vertical synchronizing signal (VD: Vertical Driving) from a sensor is required for one feedback control. Image data for one screen is loaded and transferred based on the vertical synchronizing signal.
Upon activation by turning on a camera, or at the start of the display of a confirmation image before photographing after actual photographing, an exposure control is generally started using a predetermined reference value or exposure information obtained in the preceding actual photographing.
Japanese Unexamined Patent Application Publication No. 2004-266362 discloses a technique in which exposure is feedback-controlled while a confirmation moving image before photographing is being displayed. In the feedback control, an automatic exposure (AE) evaluation value of an image output from an image-capturing device is referred to, and a charge storage time and the like of the image-capturing device are corrected in a direction in which exposure approaches a correct value.